Ethanol production from biological wastes
View Patent ↗The invention provides methods, apparatuses, and kits for producing ethanol and other alcohols. The methods involve fermenting organic material in a fermentation mixture to a biogas comprising methane; converting at least a portion of the biogas to synthesis gas comprising CO and H 2 ; and contacting at least a portion of the synthesis gas with a catalyst to produce alcohol. In some embodiments, a microorganism that reduces ferric iron to ferrous iron is included in the fermentation mixture to enhance the efficiency of the fermentation and the yield of alcohol. The invention also provides a method of producing alcohol involving fermenting organic material to a biogas comprising methane; removing sulfhydryls from the biogas; converting at least a portion of the biogas to synthesis gas comprising CO and H 2 ; contacting at least a portion of the synthesis gas with a sulfur-free catalyst to produce a substantially sulfur-free alcohol; and purifying the alcohol wherein the purified alcohol is substantially sulfur-free and comprises less than 5% methanol and at least 70% C 2 + alcohols by weight.
1. A method of producing alcohol comprising:
fermenting organic waste material in a fermentation mixture containing methanogenic microorganisms to a biogas comprising methane;
removing sulfhydryls from the biogas;
converting at least a portion of the biogas to synthesis gas comprising CO and H 2 ;
contacting at least a portion of the synthesis gas with a sulfur-free catalyst to produce alcohol; and
purifying the alcohol, wherein the purified alcohol comprises less than 10 ppm sulfur atoms, less than 5% methanol, and at least 70% C 2 + alcohols by weight.
2. The method of claim 1 wherein the yield of C 2 + alcohols is at least 6 gallons per 1000 cubic feet of methane in the biogas, and the conversion of volatile organics in the fermentation mixture to biogas is at least 65% efficient.
3. The method of claim 1 wherein the step of removing sulfhydryls from the biogas comprises contacting the biogas with a metal cation that binds sulfhydryls.
4. The method of claim 3 wherein the metal cation is Fe 2+ formed by reduction of Fe 3+ in the fermentation mixture by a microorganism that reduces Fe 3+ and produces at least one volatile organic acid from organic substrates.
5. The method of claim 4 wherein the fermentation mixture further comprises an iron source.
6. The method of claim 1 wherein the purified alcohol comprises less than 0.5% by weight methanol.
7. The method of claim 1 wherein the purified alcohol comprises at least 60% by weight ethanol.
8. The method of claim 1 wherein the step of purifying the alcohol comprises fractionating the alcohol into a C 2 +-rich fraction and a methanol-rich fraction, wherein the method further comprises recirculating the methanol-rich fraction into the synthesis gas for contact with the catalyst.
9. The method of claim 6 wherein the yield of C 2 + alcohols in the purified alcohol is at least 6 gallons per 1000 cubic feet of methane in the biogas, and the conversion of volatile organics in the fermentation mixture to biogas is at least 65% efficient.
10. The method of claim 1 wherein the step of converting at least a portion of the biogas to synthesis gas comprises partially oxidizing at least a portion of the biogas.
11. The method of claim 1 wherein the alcohol comprises less than 1 ppm sulfur atoms.
12. The method of claim 4 wherein the microorganism that reduces Fe 3+ is derived from ATCC 55339.
13. The method of claim 1 wherein the organic material comprises dairy manure.
14. The method of claim 1 wherein the organic material comprises hog manure, turkey manure, chicken manure, slaughterhouse waste, municipal sewage, or crop waste.